Let me share some insights about the isolating unexpected issues like this in QuickBooks Online.
Generally, when you encounter unexpected errors in QuickBooks, it's recommended to try the browser troubleshooting. This is to determine if the browser is causing the issue. At times, the stored data can cause some odd errors and simply needs to be cleared from the browser. For additional information on this and steps for supported browsers, please visit the following link: How Do I Clear My Browser Cache And Temporary Internet files?.
If doing this process doesn't make a difference, It'd be best to reach out to our Customer Care Team. They have the tools to further verify the issue and add you to the list of the affected user is there's an ongoing investigation.
Additionally, you make check out these articles below for your future reference in managing the time-sheets on your QuickBooks Online: